| dc.description.abstract | After the wide use and application of many organic chemicals the last 50 years, they have been detected in trace amounts in water and soil samples. Chemicals can be released accidentally or after their application in the environment and later can reach drinking water wells, surface water or groundwater. The chemical properties of the compound is a major factor for its distribution in the environment but also physical, chemical and biological process in the close environment are also determinant factors for chemical’s transport and degradation. The soil properties and the hydrogeology of the contaminated site affect the transport of the contaminant. In addition, chemical and biological processes can transform the chemical into harmless molecules. Different redox reactions lead to distribution of microorganism populations according to oxygen presence or nutrients. Many water disinfection techniques are used to treat the contaminants and produce safe water. One popular and economical technique, which used in many European countries, is the river bank filtration, where pumping wells near riparian areas collect water from river. It was considered as a safe water treatment process, because chemical and biological reactions during subsurface passage could reduce the amount of contaminants. However these processes are affected by climate, soil properties, geological characteristics of the aquifer, redox conditions and microbial activity, so in some cases the filtration is not efficient. Many chemicals have been found below or above the health threshold in water samples or in drinking water wells. The evaluation of the environmental fate of most chemicals and their transport and degradation under different redox conditions should be investigated, so better water treatment techniques could be developed. This review study focuses on the environmental transport and degradation studies of selected chemicals that have been widely used in the last decades. These chemicals are the methyl tert-butyl ether (MTBE), bisphenol-a (BPA), metformin, metolachlor and mecoprop. Results from this study showed that the most of them are persistent in the water and have low degradation rates in the deeper aquifers and under anaerobic conditions. Metformin was found to be fully degraded to its metabolite, Guanylurea and further studies for this chemical should be conducted. Bisphenol-a can be completely eliminated during conventional treatment techniques but not under anaerobic conditions. Some degradation of MTBE, metolachlor and mecoprop occurs under aerobic conditions. | |
